The present invention relates in general to light-emitting diodes (LEDs) and in particular to deposition of phosphor-containing material on LED dies for light color selection.
With the incandescent light bulb producing more heat than light, the world is eager for more efficient sources of artificial light. LEDs are a promising technology and are already widely deployed for specific purposes, such as traffic signals and flashlights. For colored light, an LED chip is often combined with a wavelength-converting material to obtain desired output light color. For example, yellow phosphors are often combined with blue LEDs to produce white light. However, the development of LED-based lamps for general illumination has run into various difficulties. Among these is the difficulty of mass-producing LED emitters with phosphors that provide a consistent light color.
Conventional LED emitters often include an LED die in a recess or cup structure that has phosphor-containing material in the cup. In some cases, the phosphor-containing material is separated from the LED die by, for example, a silicone material. These conventional methods tend suffer from many drawbacks. For example, conventional methods often use a large amount of phosphor, and they may cause poor cooling of the phosphor and the silicone material. As a result, the emitter can suffer from less reliable packaging and non-uniform angular distribution of light color. Given existing processes for LED manufacture, mass-producing white LEDs with a consistent color temperature has proven to be a challenge.